When the colossal Hoover Dam rose during the years from 1931 to 1935, much more was built than an engineering marvel; it became a badge of ingenuity and human endurance at the core of the Great Depression. At the heart of this structure was an innovative concrete curing method that would set up a milestone for almost ninety years since completion.
The longevity of the dam depends on how good the curing process of the concrete core of the dam is. Engineers of that period estimated that it would have taken up to 100 years for the concrete to completely cure because of the large size of the dam and because of the heat generated by the curing process. As one expert explained, “If the dam had been constructed in a single pour, the concrete would have gotten so hot that it would have taken 125 years for the concrete to cool to ambient temperatures.”
To combat this challenge, the Hoover Dam was built not as a monolith but in a series of individual trapezoidal columns, allowing heat to dissipate more effectively. The concrete also included a network of 582 miles of 1-inch steel pipe that first circulated river water and later chilled water from a refrigeration plant capable of “producing 1,000 tons of ice in 24 hours.”
The statistics regarding the construction are overwhelming. The amount of concrete in the dam totals “4,360,000 cubic yards,” and if all materials used were placed on a train, “as the engine entered the switch yards in Boulder City, the caboose would just be leaving Kansas City, MO.”
At this time of the Great Depression, such a colossus could be constructed only by an effort costing an amount no company could afford to execute by itself. The project was won by a consortium of construction companies with a $48.8 million bid, which was, at the time, the largest contract the federal government had ever awarded.
Equally impressive was the amount of workforce required for the construction of the dam, with some 21,000 men employed and an average of 3,500 workers per day, peaking at more than 5,200 laborers during June 1934. The “first concrete for the dam was placed on June 6, 1933,” and the “last on May 29, 1935,” at an average of “160,000 cubic yards of concrete placed in the dam per month” and a peak of “10,462 cubic yards in one day.”
Besides its basic functions of flood control, water diversion, and hydroelectric power generation, the Hoover Dam merits a place in architectural history in America as much larger in masonry mass than the Great Pyramid of Giza. This structure became an enduring symbol of innovation and industrial prowess.